Filter devices of the general type under consideration include filter bags coated internally with diatomite or the like and adapted for fluid flow outwardly therethrough in a filter operation. While such devices have proven generally satisfactory, certain disadvantages have been encountered in operation. More particularly, ballooning of the bags under internal pressure followed by contraction on pressure relief through enlarged filter openings, and once again followed by ballooning has been an undesirable characteristic of such devices. Intermittent ballooning the resulted in the passage of undesirably large particles through the filter openings in the bag and, when the bags are arranged in closely spaced relationship, serious abrasion wear of the bags has occurred as they engage each other during the ballooning phase. Still further, the mounting of filter bags and their supporting structure about inlet flanges has been undesirably complex and somewhat unwieldy in filter devices heretofor available.